JP2012064403A - Charged particle beam irradiation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charged particle beam irradiation device which can improve the efficiency of beam utilization by reducing an unused amount of beams.SOLUTION: An irradiation field forming unit 500 includes a scanning electromagnet which scans a charged particle beam emitted from a synchrotron 200 in a direction perpendicular to the beam advance direction. An irradiation order determination system 63 of a control unit 600 predicts a circling beam amount which will be lost when a circling beam being accelerated for some energy is reaccelerated or decelerated for another energy, and, by using a circling beam charge amount measured by a circling beam charge amount monitor 25 and an irradiation dose measured by an irradiation dose monitor 52, changes the operation pattern of the synchrotron so as to minimize the lost circling beam amount through entire irradiation, thereby determining the order of energy to be irradiated with.

Description

  The present invention relates to a charged particle beam irradiation apparatus, and more particularly to a charged particle beam irradiation apparatus suitable for application to a particle beam therapy apparatus that irradiates an affected area with an ion beam such as protons and carbon ions.

Reflecting the recent aging society, as one of the cancer treatment methods, radiotherapy that is minimally invasive, has less burden on the body, and can maintain a high quality of life after treatment is attracting attention. Among them, a particle beam therapy system using charged particle beams such as protons and carbon ions accelerated by an accelerator is particularly promising because of excellent dose concentration on the affected area. The particle therapy system is based on an accelerator such as a synchrotron that accelerates the charged particle beam generated by the ion source to near the speed of light, a beam transport system that transports the charged particle beam emitted from the accelerator, and the position and shape of the affected part. The irradiation apparatus is configured to irradiate a patient with a charged particle beam.
Conventionally, in an irradiation apparatus of a particle beam therapy system, when a charged particle beam is irradiated in accordance with the shape of an affected part, the beam diameter is enlarged by a scatterer, and then the peripheral part is shaved by a collimator to shape the charged particle beam. However, in the irradiation method using a scatterer, there are problems such that generation of neutrons cannot be reduced and the degree of coincidence between the affected part shape and the irradiation region cannot be improved. Therefore, in recent years, as a more accurate irradiation method, there is an increasing market need for a scanning irradiation method in which a charged particle beam having a small diameter is taken out from an accelerator, deflected by an electromagnet, and scanned according to the shape of an affected area.

  In the scanning irradiation method, a three-dimensional affected part shape is divided into a plurality of layers in the depth direction, and each layer is further divided two-dimensionally. In the depth direction, the energy of the charged particle beam is changed to selectively irradiate each layer, and in each layer, the charged particle beam irradiated by the electromagnet is two-dimensionally scanned to give a predetermined dose to each irradiation spot. A method of continuously irradiating during movement between irradiation spots is called raster scanning, while a method of stopping the irradiation beam during movement is called discrete spot scanning.

  Conventionally, when the scanning irradiation method is used, the layer is irradiated in one cycle of the synchrotron operation (the period from the incidence of the charged particle beam to the synchrotron until the irradiation target is ready for the next incidence). Was only one layer, and the circular beam remaining in the synchrotron was not used for irradiation when irradiation to the layer was completed. In the conventional scanning irradiation method, many circling beams are not used for irradiation in the layer where the required dose is small, and it is difficult to improve the beam utilization efficiency (the ratio of the circulating beams accelerated by the synchrotron used for irradiation). Met.

  On the other hand, there are known a method of changing the energy of an orbiting beam in one cycle of synchrotron operation (see, for example, Patent Document 1) and a method of changing the energy of an orbiting beam in a cycle (see, for example, Patent Document 2). It has been.

Japanese Patent No. 33007059 JP 2008-226740 A

  When reaccelerating or decelerating from one energy to another during one cycle of synchrotron operation, it is necessary to change the operating parameters of the synchrotron (for example, deflection magnet magnetic field strength, acceleration cavity voltage, etc.) A part of the beam is lost. The amount of beam lost in the entire irradiation is determined by the number of times of energy change and the order thereof. However, in the conventional operation methods described in Patent Document 1 and Patent Document 2, the order determination policy of the layers to be irradiated in one cycle is not clear. There was a risk that the beam loss amount would increase in order. In addition, when determining the next irradiation layer, it was not possible to make a determination according to the amount of the circulating beam remaining in the synchrotron, and there was a risk that the amount of beam loss would increase due to an increase in the number of times of energy change in the entire irradiation. . Furthermore, due to the beam loss due to this energy change, there are cases where the circular beam remaining in the synchrotron cannot be irradiated. Due to the above, the treatment time may be prolonged due to a decrease in beam utilization efficiency due to an increase in a beam that is accelerated but not used for irradiation to the affected part (hereinafter referred to as an unused beam).

  An object of the present invention is to provide a charged particle beam irradiation apparatus that can reduce the amount of unused beams and improve beam utilization efficiency.

(1) In order to achieve the above object, the present invention scans a synchrotron that accelerates and emits a charged particle beam, and the charged particle beam emitted from the synchrotron in a direction perpendicular to the beam traveling direction. An irradiation field forming device having a scanning electromagnet, an orbiting beam charge monitor for measuring the orbiting beam charge of the synchrotron, an irradiation dose monitor for measuring the irradiation dose, and the state in which the orbiting beam is accelerated to a certain energy Predicting the amount of orbiting beam lost when reacceleration or re-deceleration to the energy of, using the orbiting beam charge amount measured by the orbiting beam charge monitor and the irradiation dose measured by the irradiation dose monitor The irradiation pattern is changed by changing the synchrotron operation pattern so that the amount of circulating beam lost throughout the irradiation is minimized. It is obtained by such a control device having an illumination sequence determination section which determines the order of Energy.
With this configuration, it is possible to reduce the amount of unused beams and improve the beam utilization efficiency in the charged particle beam irradiation apparatus.

  (2) In the above (1), preferably, the irradiation order determination unit has a minimum amount of circulating beam predicted to be lost until the irradiation in the next period and thereafter is completed at the time when irradiation with a certain energy is completed. Thus, the operation pattern is changed.

  (3) In the above (2), preferably, the irradiation order determining unit, when the irradiation with a certain energy is completed, the amount of circulating beam not used for irradiation within the operation period of the synchrotron at that time The operation pattern is changed so as to be minimized.

  (4) In the above (1), preferably, when the irradiation order determining unit determines that there is a layer that can be irradiated within the same period when irradiation with a certain energy is completed, the next irradiation layer is determined. If there is only one layer that satisfies the first condition in which the amount of orbital beam charge that is expected to remain after irradiation is less than the amount of beam loss at the time of energy change, that layer is determined as the next irradiation layer. It is a thing.

  (5) In the above (1), preferably, when the irradiation order determining unit determines that there is a layer that can be irradiated within the same period when irradiation with a certain energy is completed, the next irradiation layer is determined. When there are a plurality of layers satisfying the first condition in which the amount of orbital beam charge expected to remain after irradiation is equal to or less than the amount of beam loss at the time of energy change, the layer with the highest unirradiated dose is determined as the next irradiation layer It is a thing.

  (6) In the above (1), preferably, when the irradiation order determining unit determines that there is a layer that can be irradiated within the same period when irradiation with a certain energy is completed, the next irradiation layer is determined. If there is no layer that satisfies the first condition where the amount of orbiting beam charge that is expected to remain after irradiation is equal to or less than the amount of beam loss at the time of energy change, it is predicted that it will remain after irradiation based on the amount of orbiting beam at that time When there is a combination of layers satisfying the second condition where the amount of circulating beam charge is less than the amount of beam loss at the time of energy change, one layer in the combination satisfying the second condition is determined as the next irradiation layer It is a thing.

  (7) In the above (1), preferably, when the irradiation order determining unit determines that there is a layer that can be irradiated within the same period when irradiation with a certain energy is completed, the next irradiation layer is selected. If there is no layer that satisfies the first condition where the amount of orbiting beam charge that is expected to remain after irradiation is equal to or less than the amount of beam loss at the time of energy change, it is predicted that it will remain after irradiation based on the amount of orbiting beam at that time When there are a plurality of layer combinations that satisfy the second condition in which the amount of rounded beam charge is less than or equal to the beam loss amount at the time of energy change, the combination that is expected to minimize the beam that is not used for irradiation is selected. It is a thing.

According to the present invention, the amount of unused beams can be reduced and the beam utilization efficiency can be improved.

It is a conceptual diagram which shows the whole structure of the charged particle beam irradiation apparatus by one Embodiment of this invention. It is a conceptual diagram which shows the structure of the irradiation field forming apparatus used for the charged particle beam irradiation apparatus by one Embodiment of this invention. It is operation | movement explanatory drawing of the irradiation field forming apparatus used for the charged particle beam irradiation apparatus by one Embodiment of this invention. It is a block which shows the structure of the control apparatus used for the charged particle beam irradiation apparatus by one Embodiment of this invention. It is a timing chart which shows the operation | movement procedure of one period of the synchrotron in the charged particle beam irradiation apparatus by one Embodiment of this invention. It is a flowchart which shows the operation | movement procedure of one period of the synchrotron in the charged particle beam irradiation apparatus by one Embodiment of this invention. It is a timing chart which shows the operation | movement procedure of one period of the synchrotron in the charged particle beam irradiation apparatus by one Embodiment of this invention. It is explanatory drawing of the method of estimating the reduction | decrease amount of an orbital beam amount, when reaccelerating or decelerating from one energy to another energy in the charged particle beam irradiation apparatus by one Embodiment of this invention. 6 is a flowchart illustrating a method for determining a next irradiation layer based on the amount of circulating beams at the time when irradiation with respect to a certain layer is completed in the charged particle beam irradiation apparatus according to the embodiment of the present invention. In the charged particle beam irradiation apparatus by one Embodiment of this invention, it is explanatory drawing of the specific example of the method of determining the next irradiation layer based on the amount of round beams at the time of irradiation completion with respect to a certain layer. In the charged particle beam irradiation apparatus by one Embodiment of this invention, it is explanatory drawing of the specific example of the method of determining the next irradiation layer based on the amount of round beams at the time of irradiation completion with respect to a certain layer. FIG. 12 is an explanatory view of a change in the amount of excitation of the deflection electromagnet over the entire irradiation period when the method for determining the next irradiation layer shown in FIGS.

Hereinafter, the configuration and operation of a charged particle beam irradiation apparatus according to an embodiment of the present invention will be described with reference to FIGS.
First, the overall configuration of the charged particle beam irradiation apparatus according to the present embodiment will be described with reference to FIG.
FIG. 1 is a conceptual diagram showing an overall configuration of a charged particle beam irradiation apparatus according to an embodiment of the present invention.

  The charged particle beam irradiation apparatus 100 of this embodiment irradiates a charged particle beam (for example, proton beam) to the affected part of the patient 41 fixed to the treatment bed 42. The charged particle beam irradiation apparatus 100 includes a synchrotron 200 that emits after accelerating a charged particle beam preliminarily accelerated by a pre-accelerator 11 such as a linac to a predetermined energy, and a charged particle beam emitted from the synchrotron 200. A beam transport system 300 that leads to 400, an irradiation field forming device 500 that irradiates a charged particle beam in accordance with the shape of the affected part (irradiation target) of the patient 41 in the treatment room 400, and a control device 600.

  The synchrotron 200 includes an incident device 21 that receives a charged particle beam preliminarily accelerated by the pre-accelerator 11 and a plurality of deflections that deflect a charged particle beam (circular beam) that circulates in the synchrotron 200 and circulate on a fixed orbit. An electromagnet 22, a plurality of quadrupole electromagnets 23 that apply a horizontal and vertical focusing force so that the circular beam does not spread, a plurality of acceleration cavities 24 that accelerate the circular beam to a predetermined energy with a high-frequency acceleration voltage, and the charge of the circular beam A circulating beam amount monitor 25 for measuring the amount, a plurality of hexapole electromagnets 26 that form a stability limit with respect to the vibration amplitude of the circulating beam, and an output that increases the vibration amplitude of the circulating beam in a high-frequency electromagnetic field to exceed the stability limit. The device 27 and an output deflecting device for deflecting the circulating beam exceeding the stability limit with an electrostatic field or a static magnetic field and taking it out of the synchrotron 200 And it consists of 28.

Next, the configuration and operation of the irradiation field forming apparatus 500 used in the charged particle beam irradiation apparatus according to the present embodiment will be described with reference to FIGS.
FIG. 2 is a conceptual diagram showing a configuration of an irradiation field forming apparatus used in the charged particle beam irradiation apparatus according to the embodiment of the present invention. The same reference numerals as those in FIG. 1 indicate the same parts. FIG. 3 is an operation explanatory view of an irradiation field forming apparatus used in the charged particle beam irradiation apparatus according to the embodiment of the present invention.

  As shown in FIG. 2, the irradiation field forming apparatus 500 deflects the charged particle beam guided by the beam transport system 300 shown in FIG. 1 in the horizontal and vertical directions, and two-dimensionally matches the cross-sectional shape of the affected part 41a. The scanning electromagnets 51a and 51b for scanning, an irradiation dose monitor 52 for measuring the amount of the charged particle beam that has passed, and a beam position monitor 53 for measuring the position of the charged particle beam that has passed.

  Next, the scanning irradiation method used as the irradiation method by the particle beam therapy system 100 of the present embodiment will be described with reference to FIG. FIG. 3 is a view seen from the upstream side of the charged particle beam that irradiates one layer of the affected part 41a divided in the depth direction (z direction in FIG. 2).

  The three-dimensional affected part shape is divided into a plurality of layers in the depth direction, and each layer is selectively irradiated by changing the energy of the emitted beam of the synchrotron 200. In each layer, as shown in FIG. 3, a scanning electromagnet 51 scans the irradiation beam two-dimensionally (x direction, y direction) to give a predetermined dose to each part in the layer.

Next, the configuration and operation of the control device 600 used in the charged particle beam irradiation apparatus according to the present embodiment will be described with reference to FIG.
FIG. 4 is a block diagram showing a configuration of a control device used in the charged particle beam irradiation apparatus according to the embodiment of the present invention. The same reference numerals as those in FIG. 1 indicate the same parts.

  The control device 600 includes a treatment planning device 61, a central control device 62, an accelerator control device 64, an irradiation control device 65, and a display device 66. The treatment planning device 61 determines irradiation conditions for forming an appropriate irradiation field in the affected area 41a. The central controller 62 has various set values for the pre-stage accelerator 11, the synchrotron 200, the beam transport system 300, and the irradiation field forming device 500. The accelerator controller 64 controls the front stage accelerator 11, the synchrotron 200, and the beam transport system 300. The irradiation control device 65 controls the irradiation field forming device 500. On the display device 66, the irradiation dose in the depth direction is sequentially displayed. The control device 600 is connected to the front stage accelerator 11, the synchrotron 200, the beam transport system 300, and the irradiation field forming device 500, and controls the operation of each device by controlling the power supply (not shown) of each device. .

  The accelerator control device 64 inputs the circular beam amount measured by the circular beam amount monitor 25 and the irradiation control device 64 inputs the irradiation dose measured by the irradiation dose monitor 52 to the central control device 62. The central controller 62 has an irradiation order determination system 63 that determines an operation pattern based on the amount of circulating beams and the amount of irradiation charges. The treatment planning device 61 creates a set value of the target irradiation dose for each irradiation layer in advance based on the type and shape of the affected part 41a, and the central control device 62 reads the information created by the treatment planning device 61 and stores it in memory. 62a is read.

Next, the operation procedure of one cycle of the synchrotron 200 in the charged particle beam irradiation apparatus according to the present embodiment will be described with reference to FIG.
FIG. 5 is a timing chart showing an operation procedure of one cycle of the synchrotron in the charged particle beam irradiation apparatus according to the embodiment of the present invention.

  The vertical axis in FIG. 5 (A) shows the orbiting beam energy, FIG. 5 (B) shows the deflection magnet excitation amount, FIG. 5 (C) shows the orbiting beam amount, and FIG. 5 (D) shows the outgoing beam current amount. Indicates. The horizontal axis in FIG. 5 is time.

  FIG. 5 shows an operation pattern when two particles are irradiated with a charged particle beam. The operation pattern of the deflecting electromagnet 22 (operation pattern of the synchrotron 200) is composed of an incident period, an acceleration period, an emission period, a reacceleration / deceleration period, and a deceleration period as shown in FIG. Periodic operation is performed with one cycle from the start of the period to the end of the deceleration period.

  The charged particle beam from the front stage accelerator 11 is incident on the orbit of the synchrotron 200 during the incident period, and is accelerated to the target energy E1 during the acceleration period as shown in FIG. In the emission period, as shown in FIG. 5B, the amount of excitation of the deflection electromagnet 22 is constant, but the amount of excitation of the quadrupole electromagnet 23 and the hexapole electromagnet 26 is changed, and the betatron oscillation of the circulating beam becomes unstable. A region (separatrix) is formed. The oscillation amplitude of the circulating beam is increased by the high-frequency electromagnetic field generated by the extraction device 27 to exceed the stability limit, and the beam is taken out from the synchrotron using the output deflection device 28, and beam scanning is performed on the layer corresponding to the energy E1. As a result, as shown in FIG. 5D, the outgoing beam current flows during the outgoing period, and the amount of circulating beam gradually decreases as shown in FIG. 5C. During the emission period, the irradiation dose is sequentially measured by the irradiation dose monitor 52, and when the irradiation of the planned dose of the layer corresponding to the energy E1 stored in the memory 62a is completed, the beam emission is stopped. The orbiting beam amount monitor 25 sequentially measures the orbiting beam amount (accumulated beam amount) during operation and outputs it to the acceleration control device 64. The acceleration control device 64 outputs the circulating beam amount to the central control device 62.

  When the irradiation of the planned dose of the layer corresponding to the energy E1 is completed, the irradiation order determination system 63 recirculates or decelerates the current energy (E1) from the current energy (E1) to another energy based on the current amount of the circulating beam. The amount of decrease is predicted, and compared with the unirradiated dose of the unirradiated layer, the layer (energy) to be irradiated next is determined.

  Based on the determination of the next irradiation layer by the irradiation order determination system 63, the central controller 62 outputs each set value to the accelerator controller 64 and the irradiation controller 65. In the re-acceleration / deceleration period, as shown in FIG. 5A, the circulating beam is re-accelerated or decelerated to the next irradiation energy E2, and beam scanning is performed on the layer corresponding to the energy E2 in the emission period. When the irradiation of the planned dose to the layer corresponding to the energy E2 is completed, the irradiation order determination system 63 again determines the layer to be irradiated next. If there is no layer that can be irradiated next, the incident beam as shown in FIG. Decrease the amount of excitation of the bending magnet to the energy of and move to the next cycle.

Next, the operation procedure of one cycle of the synchrotron 200 in the charged particle beam irradiation apparatus according to the present embodiment will be described with reference to FIGS.
FIG. 6 is a flowchart showing an operation procedure of one cycle of the synchrotron in the charged particle beam irradiation apparatus according to the embodiment of the present invention. FIG. 7 is a timing chart showing an operation procedure of one cycle of the synchrotron in the charged particle beam irradiation apparatus according to the embodiment of the present invention.

  In step S10, after the beam is incident on the synchrotron, in step S20, the orbiting beam is accelerated (or decelerated) to the energy corresponding to the irradiation layer set in advance by the irradiation order determination system 63.

  After completion of acceleration, in step S30, the target irradiation dose set by the treatment planning apparatus is irradiated. In addition, the layer (layer) with the largest planned irradiation dose that the irradiation order determination system 63 minimizes the unused beam is set as the first irradiation layer in advance for the first irradiation after the start of treatment.

  When irradiation is completed in step S40, the circulating beam quantity monitor 25 measures the circulating beam quantity (accumulated beam quantity: accumulated charge quantity) in step S50.

  In step S60, the irradiation order determination system 63 determines whether there is a layer that can move to the next irradiation with the amount of circulating beam (accumulated charge amount) remaining at that time.

  If any energy of the incomplete irradiation layer is taken into consideration, it is predicted that there will be no circular beam remaining due to the beam loss due to the energy change, and if the next irradiation cannot be performed, the irradiation order determination system 63 performs the next in step S80. The first irradiation layer of the cycle is determined, and the process proceeds to the next cycle in step S90. Note that a method of predicting a decrease in the amount of circulating beam when reaccelerating or decelerating from one energy to another will be described later with reference to FIG.

  In the case where there are enough orbiting beams and the next irradiation can be performed, a next irradiation layer is determined by the irradiation order determination system 63 in step S70. A specific example of how to determine the next irradiation layer will be described in detail with reference to FIG. In accordance with this determination, the process returns to step S20 to accelerate or decelerate again and irradiate the set dose.

  When the irradiation is completed, the amount of the circulating beam is measured in step S50, and the presence or absence of an irradiable layer is determined in step S60 as in the above procedure. When there is no irradiable layer, the first irradiation layer is determined so that the amount of the unused beam is minimized in the irradiation after that point, and the next period starts. At that time, considering the loss of the circulating beam due to the energy change, the first irradiation layer is determined from the irradiation order that minimizes the unused beam. In order to avoid an event in which the number of beams incident on the synchrotron 200 is less than expected and the irradiation to the first irradiation layer cannot be completed, the first irradiation again is performed when the amount of the circulating beam is insufficient for the irradiation of the first irradiation layer. The irradiation layer may be determined.

  FIG. 7 shows an operation pattern when the periodic operation is repeated according to the flow shown in FIG.

Next, with reference to FIG. 8, a method for predicting a decrease amount of the orbiting beam amount when reaccelerating or decelerating from one energy to another energy in the charged particle beam irradiation apparatus according to the present embodiment will be described.
FIG. 8 is an explanatory diagram of a method for predicting a decrease amount of the orbiting beam when reacceleration or deceleration from one energy to another energy in the charged particle beam irradiation apparatus according to the embodiment of the present invention.

  The central controller 62 has, as a data table, the memory 62a as a data table of the loss rate of the circulating beam amount when the energy is reaccelerated or decelerated from one energy to another.

  FIG. 8 shows an example of a data table used when predicting the amount of circular beam loss. The first column of the table represents the energy before the energy change, and the first row represents the energy after the energy change. The other terms mean the orbital beam loss rate predicted at the time of energy change. More specifically, when reacceleration or deceleration from energy Em to energy En during one synchrotron operation cycle, it can be predicted that Lmn of the circulating beams will be lost. This data table may be created on the basis of actual measurement values, or may be obtained using simulation calculation, complementation by simulation calculation of the interval between measurement points, or learning from past results.

  In FIG. 8, the data table is represented by using the orbiting beam loss rate Lmn. However, instead of the orbiting beam loss rate Lmn, a data table of the orbiting beam loss amount may be created for each orbiting beam amount. is there.

Next, referring to FIG. 9, in the charged particle beam irradiation apparatus according to the present embodiment, a method for determining the next irradiation layer based on the amount of the circulating beam at the time when irradiation with respect to a certain layer is completed (step of FIG. 6). A detailed method of S70 will be described. A specific example using this method will be described later with reference to FIGS.
FIG. 9 is a flowchart showing a method for determining the next irradiation layer based on the amount of the circulating beam at the time when irradiation with respect to a certain layer is completed in the charged particle beam irradiation apparatus according to the embodiment of the present invention.

  In step S60 of FIG. 6, when it is determined that there is a layer that can be irradiated within the same period when irradiation with a certain energy is completed, first, in step S71, it is predicted to remain after irradiation of the next irradiation layer. A layer is searched for such that the amount of circular beam charge to be applied is equal to or less than the amount of beam loss at the time of energy change (hereinafter referred to as “condition A”).

  In step S72, when there is only one layer satisfying the condition A, the layer is determined as the next irradiation layer.

  In Step S73, when there are a plurality of layers satisfying the condition A, the layer with the largest unirradiated dose is determined as the next irradiated layer.

  If there is no layer satisfying the condition A, in step S74, based on the amount of circulating beam at that time, the amount of circulating beam charge that is expected to remain after irradiation is equal to or less than the beam loss amount at the time of energy change (hereinafter, “ A combination of layers such as “condition B” is searched.

  If there is a layer that satisfies the condition B, in step S75, one layer in the combination that satisfies the condition B is determined as the next irradiation layer. If there are a plurality of combinations that satisfy the condition B, a combination that is predicted to minimize the beam that is not used for irradiation is selected in step S75. When determining the next irradiation layer from the combination that satisfies the condition B, the irradiation time can be shortened by determining the first irradiation layer in the order that takes the least time for irradiation as the next irradiation layer.

  If there is no combination that satisfies the condition B, in step S76, a layer having the largest unirradiated dose among the unirradiated layers is determined as the next irradiated layer. At this time, the irradiation of the layer may not be completed within the amount of the circulating beam. In that case, the layer that has not been irradiated in this cycle is treated as the next irradiation layer candidate equivalently to other layers thereafter.

  By repeating the determination process as described above, the irradiation order in each cycle is optimized so that the total sum of beams not used for irradiation is minimized, and the beam utilization efficiency is improved.

  In addition, in order to avoid an event that the planned dose cannot be irradiated within the cycle due to the beam loss amount slightly deviating from the prediction, “Condition A” is predicted to remain {(after irradiation of the next irradiation layer). The layer that satisfies the following condition: the amount of circular beam charge) ≦ (beam loss during energy change) + (safety width)} may be determined. Similarly, the “condition B” may be {(circular beam charge amount expected to remain after irradiation of the combination) ≦ (beam loss amount at energy change) + (safety width)}.

Next, in FIG. 10 and FIG. 11, in the charged particle beam irradiation apparatus according to the present embodiment, a specific method for determining the next irradiation layer based on the amount of the circulating beam at the time when irradiation with respect to a certain layer is completed. An example will be described.
10 and 11 show a specific example of a method for determining the next irradiation layer based on the amount of the circulating beam at the time when irradiation with respect to a certain layer is completed in the charged particle beam irradiation apparatus according to the embodiment of the present invention. It is explanatory drawing.

  The operation method when the target irradiation dose for each layer created by the treatment planning device 61 is as shown in FIGS. 10 and 11 will be described. The horizontal axis of the graph of FIG. 10 is the layer number, the vertical axis is the target irradiation dose, and the target irradiation dose for each layer corresponds to the values in the table of FIG. Also, the thick line in the graph of FIG. 10 means the amount of circulating beam that can be accumulated in the synchrotron 200, and corresponds to the maximum amount of circulating beam in the table of FIG. The operation method will be described assuming that the loss amount of the orbiting beam due to the energy change is “1” (same as the beam amount unit in FIG. 9). In this example, when there are a plurality of options of the next irradiation layer that minimizes the unused beam, the layer having the highest energy among the options, that is, the layer having the largest layer number is selected as the next irradiation layer.

  First, the layer 11 that is the layer having the maximum unirradiated dose is irradiated. When the irradiation of the layer 11 is completed, the amount of the circulating beam is “2”. Since the amount of orbital beam loss due to the energy change is “1”, the amount of orbital beam charge expected to remain after irradiation of the next irradiation layer becomes 1 or less when the layers 1, 2, 3, and 4 are irradiated. This is the case. The beam utilization efficiency is the same regardless of which layer is selected, but layer 4 is determined as the next irradiation layer. The amount of the circulating beam remaining after the irradiation of layer 4 is 0, and further irradiation is impossible, so the next cycle is started.

  Subsequently, the layer 10 that is the layer having the maximum unirradiated dose at this time is irradiated. When the irradiation of the layer 10 is completed, the amount of the circulating beam becomes “4”. Since the amount of orbital beam loss due to the energy change is “1”, the amount of orbital beam charge expected to remain after irradiation of the next irradiation layer is 1 or less when the layers 5, 6, 7 and 8 are irradiated. Is the case. Since layer 8 has the highest unirradiated dose, the next irradiation layer is determined to be layer 8. The amount of the circulating beam remaining after layer 8 irradiation is 0, and further irradiation is impossible, so the next period starts.

  Subsequently, the layer 9, which is the layer having the maximum unirradiated dose at this time, is irradiated. When the irradiation of the layer 9 is completed, the amount of the circulating beam is “5”, but there is no layer that satisfies the condition A. The combinations that satisfy condition B are (Layer 1, Layer 2), (Layer 1, Layer 3), (Layer 1, Layer 5), (Layer 1, Layer 6), (Layer 1, Layer 7), (Layer 2) , Layer 3), (layer 2, layer 5), (layer 2, layer 6), (layer 2, layer 7), (layer 3, layer 5), (layer 3, layer 6), and (layer 3, 12 sets of layers 7). The sets in which the amount of circular beam charge predicted to remain after irradiation is minimized are (Layer 1, Layer 5), (Layer 1, Layer 6), (Layer 1, Layer 7), (Layer 2, Layer 5), Nine sets of (Layer 2, Layer 6), (Layer 2, Layer 7), (Layer 3, Layer 5), (Layer 3, Layer 6) and (Layer 3, Layer 7), but energy change time reduction Therefore, the layer 7 is determined as the next irradiation layer. When the irradiation of layer 7 is completed, the amount of the circulating beam becomes “2”, and from condition A, layer 3 is determined as the next irradiation layer. The amount of the circulating beam remaining after layer 3 irradiation is 0, and further irradiation is impossible, so the next period starts.

  Subsequently, the layer 6, which is the layer having the maximum unirradiated dose at this time, is irradiated. At the time when the irradiation of the layer 6 is completed, the circulating beam amount is “8”, but there is no irradiation incomplete layer that satisfies the condition A. The combination that satisfies the condition B is a combination that irradiates all the remaining layers, and in order to shorten the energy change time, the layer 5 is determined as the next irradiation layer. Similarly, irradiation is performed in the order of layer 3, layer 2, and layer 1. When the irradiation of the layer 1 is completed, the irradiation of the scheduled dose is completed, so the treatment is terminated.

Next, with reference to FIG. 12, in the charged particle beam irradiation apparatus according to the present embodiment, changes in the deflection electromagnet excitation amount over the entire irradiation period when the method for determining the next irradiation layer in FIGS. 10 and 11 is used will be described. To do.
FIG. 12 is a diagram for explaining a change in the amount of excitation of the deflecting magnet over the entire irradiation period when the method for determining the next irradiation layer in FIGS. 10 and 11 is used in the charged particle beam irradiation apparatus according to the embodiment of the present invention. It is.

  In FIG. 12, the solid line indicates the change in the deflection electromagnet excitation amount over the entire irradiation period by the method described with reference to FIGS. 10 and 11. For comparison, the broken line indicates a change in the excitation amount of the deflecting electromagnet when irradiation is performed in order from the layer having the highest energy, that is, the layer having the highest layer number.

  In FIG. 12, the deflection electromagnet excitation amount corresponds to the beam energy in FIG. The time required for acceleration (excitation increase) is 1 time per energy, the time required for irradiation is 1 time per dose, and the time required for deceleration (decrease excitation amount) is 1 time per energy. ing.

  First, the change in the deflection electromagnet excitation amount over the entire irradiation period by the method described with reference to FIGS. 10 and 11 indicated by the solid line will be described.

  First, the deflection magnet excitation amount is accelerated to “11”. This corresponds to the beam energy amount “11” of the layer 11 in FIG. In this state, the excitation amount is held for time 8. This is the time required for the scheduled irradiation dose of the layer 11 because it is “8”. In FIG. 12, numerical symbols “L11” and “8” indicate the above-described irradiation state. The numerical symbols in parentheses indicate the irradiation status in the comparative example.

  Next, the deflection electromagnet excitation amount is decelerated to “4”. This corresponds to the beam energy amount “4” of the layer 4 in FIG. In this state, the excitation amount is held for time 1. This is the time required for the scheduled irradiation dose of layer 4 because it is “1”.

  The first cycle irradiation is thus completed, and the deflection electromagnet excitation amount is once decelerated to “0”.

  Next, irradiation of the second period is started, and the deflection electromagnet excitation amount is accelerated to “10”. This corresponds to the beam energy amount “10” of the layer 10 in FIG. In this state, the excitation amount is maintained for time 6. This is the time required for the layer 10 because the planned irradiation dose of the layer 10 is “6”.

  Next, the deflection electromagnet excitation amount is decelerated to “8”. This corresponds to the beam energy amount “8” of the layer 8 in FIG. In this state, the excitation amount is held for time 3. This is the time required for the scheduled irradiation dose of layer 8 because it is “3”.

  The second cycle irradiation is thus completed, and the deflection electromagnet excitation amount is once decelerated to “0”.

  Next, irradiation in the third period is started, and the deflection electromagnet excitation amount is accelerated to “9”. This corresponds to the beam energy amount “9” of the layer 9 in FIG. In this state, the excitation amount is held for time 5. This is the time required for the scheduled irradiation dose of layer 9 because it is “5”.

  Next, the deflection electromagnet excitation amount is decelerated to “7”. This corresponds to the beam energy amount “7” of the layer 7 in FIG. In this state, the excitation amount is held for time 2. This is the time required for the scheduled irradiation dose of layer 7 because it is “2”. Further, the deflection electromagnet excitation amount is decelerated to “3”. This corresponds to the beam energy amount “3” of layer 3 in FIG. In this state, the excitation amount is held for time 1. This is the time required for the scheduled irradiation dose of layer 3 because it is “1”.

  The third cycle irradiation is thus completed, and the deflection electromagnet excitation amount is once decelerated to “0”.

  Next, irradiation in the fourth period is started, and the deflection electromagnet excitation amount is accelerated to “6”. This corresponds to the beam energy amount “6” of the layer 6 in FIG. In this state, the excitation amount is held for time 2. This is the time required for the scheduled irradiation dose of layer 6 because it is “2”.

  Next, the deflection electromagnet excitation amount is decelerated to “5”. This corresponds to the beam energy amount “5” of the layer 5 in FIG. In this state, the excitation amount is held for time 2. This is the time required for the scheduled irradiation dose of layer 5 since it is “2”. Furthermore, the deflection magnet excitation amount is decelerated to “2”. This corresponds to the beam energy amount “1” of layer 2 in FIG. In this state, the excitation amount is held for time 1. This is the time required for the scheduled irradiation dose of layer 2 because it is “1”. Furthermore, the deflection magnet excitation amount is decelerated to “1”. This corresponds to the beam energy amount “1” of layer 1 in FIG. In this state, the excitation amount is held for time 1. This is the time required for the scheduled irradiation dose of layer 1 because it is “1”.

  The fourth period irradiation is thus completed, and the deflection electromagnet excitation amount is once decelerated to “0”. Thereby, all the irradiation from the layer 11 to the layer 1 is completed.

  Next, a case of a comparative example indicated by a broken line will be described. In the comparative example, irradiation is performed in the order of layer 11, layer 10, and layer 9.

  First, the deflection magnet excitation amount is accelerated to “11”. This corresponds to the beam energy amount “11” of the layer 11 in FIG. In this state, the excitation amount is held for time 8. This is the time required for the scheduled irradiation dose of the layer 11 because it is “8”.

  Next, the deflection electromagnet excitation amount is decelerated to “10”. This corresponds to the beam energy amount “10” of the layer 10 in FIG. In this state, the excitation amount is held for time 1. This is the time required for the irradiation because the planned irradiation dose of the layer 10 is “6” but the remaining amount of the circulating beam that can be used for the irradiation is “1”.

  The first cycle irradiation is thus completed, and the deflection electromagnet excitation amount is once decelerated to “0”.

  Next, irradiation of the second period is started, and the deflection electromagnet excitation amount is accelerated to “10”. This corresponds to the beam energy amount “10” of the layer 10 in FIG. In this state, the excitation amount is held for time 5. This is the time required to irradiate the remaining “5” because the irradiation dose “1” has already been irradiated in the previous irradiation and the scheduled irradiation dose of the layer 10 is “6”.

  Next, the deflection electromagnet excitation is decelerated to “9”. This corresponds to the beam energy amount “9” of the layer 9 in FIG. In this state, the excitation amount is held for time 4. This is the time required for irradiation because the planned irradiation dose of layer 9 is “5”, but the remaining amount of the circulating beam that can be used for irradiation is “4”.

  The second cycle irradiation is thus completed, and the deflection electromagnet excitation amount is once decelerated to “0”.

  Next, irradiation in the third period is started, and the deflection electromagnet excitation amount is accelerated to “9”. This corresponds to the beam energy amount “9” of the layer 9 in FIG. In this state, the excitation amount is held for time 1. This is the time required to irradiate the remaining “1” because the irradiation dose “4” has already been irradiated in the previous irradiation and the scheduled irradiation dose of the layer 10 is “5”.

  Next, the deflection electromagnet excitation amount is decelerated to “8”. This corresponds to the beam energy amount “8” of the layer 8 in FIG. In this state, the excitation amount is held for time 3. This is the time required for the scheduled irradiation dose of layer 8 because it is “3”. Furthermore, the deflection magnet excitation amount is decelerated to “7”. This corresponds to the beam energy amount “7” of the layer 7 in FIG. In this state, the excitation amount is held for time 2. This is the time required for the scheduled irradiation dose of layer 7 because it is “2”. Furthermore, the deflection magnet excitation amount is decelerated to “6”. This corresponds to the beam energy amount “6” of the layer 6 in FIG. In this state, the excitation amount is held for time 1. This is the time required for irradiation because the planned irradiation dose of layer 6 is “2”, but the remaining amount of the circulating beam that can be used for irradiation is “1”.

  The third cycle irradiation is thus completed, and the deflection electromagnet excitation amount is once decelerated to “0”.

  Next, irradiation in the fourth period is started, and the deflection electromagnet excitation amount is accelerated to “6”. This corresponds to the beam energy amount “6” of the layer 6 in FIG. In this state, the excitation amount is held for time 1. This is the time required to irradiate the remaining “1” because the irradiation dose “1” has already been irradiated in the previous irradiation and the scheduled irradiation dose of layer 6 is “1”.

  Next, the deflection electromagnet excitation amount is decelerated to “5”. This corresponds to the beam energy amount “5” of the layer 5 in FIG. In this state, the excitation amount is held for time 2. This is the time required for the scheduled irradiation dose of layer 5 since it is “2”. Furthermore, the deflection magnet excitation amount is decelerated to “4”. This corresponds to the beam energy amount “4” of the layer 4 in FIG. In this state, the excitation amount is held for time 1. This is the time required for the scheduled irradiation dose of layer 4 because it is “1”. Further, the deflection electromagnet excitation amount is decelerated to “3”. This corresponds to the beam energy amount “3” of layer 3 in FIG. In this state, the excitation amount is held for time 1. This is the time required for the scheduled irradiation dose of layer 3 because it is “1”. Furthermore, the deflection magnet excitation amount is decelerated to “2”. This corresponds to the beam energy amount “2” of layer 2 in FIG. In this state, the excitation amount is held for time 1. This is the time required for the scheduled irradiation dose of layer 2 because it is “1”.

  The fourth period irradiation is thus completed, and the deflection electromagnet excitation amount is once decelerated to “0”.

  Next, irradiation of the fifth period is started, and the deflection electromagnet excitation amount is accelerated to “1”. This corresponds to the beam energy amount “1” of layer 1 in FIG. In this state, the excitation amount is held for time 1. This is the time required for the scheduled irradiation dose of layer 1 because it is “1”.

  The fourth period irradiation is thus completed, and the deflection electromagnet excitation amount is once decelerated to “0”.

  In FIG. 12, as understood by comparing the solid line of the present embodiment with the broken line of the comparative example, the time required for total irradiation is shortened in the present embodiment.

  Further, the beam utilization efficiency is improved in the present embodiment, which will be described. The cause of worsening the beam utilization efficiency is a loss caused by re-deceleration (or re-acceleration) from one energy to another in order to change the irradiation layer. Therefore, if the number of re-decelerations for changing the irradiation layer is small, the beam utilization efficiency is improved.

  In the case of the present embodiment, reference symbols G1, G2,..., G7 shown in FIG. 12 are re-deceleration points for changing the irradiation layer, which is a total of seven times.

  On the other hand, in the case of the comparative example, reference numerals g1, g2,..., G9 shown in FIG.

  Therefore, in this embodiment, the number of re-decelerations for changing the irradiation layer can be reduced, and the beam utilization efficiency can be improved.

As described above, according to the present embodiment, the amount of non-use beam is minimized as a whole treatment, so that the beam utilization efficiency can be improved. In addition, the time required for the total irradiation can be shortened, the treatment time can be shortened, and the burden on the patient can be reduced.

DESCRIPTION OF SYMBOLS 100 ... Particle beam therapy apparatus 11 ... Pre-stage accelerator 200 ... Synchrotron 21 ... Incident apparatus 22 ... Deflection electromagnet 23 ... Quadrupole electromagnet 24 ... Acceleration cavity 25 ... Circumference beam amount monitor 26 ... Hexapole electromagnet 27 ... Ejection apparatus 28 ... Ejection deflection apparatus DESCRIPTION OF SYMBOLS 300 ... Beam transport system 400 ... Treatment room 41 ... Patient 41a ... Affected part 42 ... Treatment bed 500 ... Irradiation field forming device 51a, b ... Scanning magnet 52 ... Irradiation dose monitor 53 ... Beam position monitor 600 ... Control device 61 ... Treatment planning device 62 ... Central controller 62a ... Memory 63 ... Irradiation order determination system 64 ... Accelerator controller 65 ... Irradiation controller 66 ... Display device

Claims (7)

A synchrotron that accelerates and emits a charged particle beam;
An irradiation field forming device having a scanning electromagnet that scans the charged particle beam emitted from the synchrotron in a direction perpendicular to the beam traveling direction;
A circulating beam charge monitor for measuring the circulating beam charge of the synchrotron;
An irradiation dose monitor for measuring the irradiation dose;
Predicting the amount of orbiting beam lost when the orbiting beam is accelerated to a certain energy and reaccelerating or decelerating to another energy, and the amount of orbiting beam charge measured by the orbiting beam charge monitor, and An irradiation order determining unit that uses the irradiation dose measured by the irradiation dose monitor to change the operation pattern of the synchrotron so as to minimize the amount of circulating beam lost throughout the irradiation and determine the order of irradiation energy. A charged particle beam irradiation apparatus comprising: a control device having: The charged particle beam irradiation apparatus according to claim 1,
The irradiation order determination unit changes the operation pattern so that the amount of circulating beam predicted to be lost before the irradiation after the next period is completed at the time when irradiation with a certain energy is completed. Characterized charged particle beam irradiation apparatus. The charged particle beam irradiation apparatus according to claim 2,
The irradiation order determination unit changes the operation pattern at the time when irradiation with a certain energy is completed, so that the amount of circulating beam not used for irradiation is minimized within the operation period of the synchrotron at that time. The charged particle beam irradiation apparatus characterized by the above-mentioned. The charged particle beam irradiation apparatus according to claim 1,
When it is determined that there is a layer that can be irradiated within the same period when irradiation with a certain energy is completed, the irradiation order determination unit is expected to remain after irradiation of the next irradiation layer A charged particle beam irradiation apparatus characterized in that, when there is only one layer that satisfies the first condition that is equal to or less than the beam loss amount when changing energy, that layer is determined as the next irradiation layer. The charged particle beam irradiation apparatus according to claim 1,
When it is determined that there is a layer that can be irradiated within the same period when irradiation with a certain energy is completed, the irradiation order determination unit is expected to remain after irradiation of the next irradiation layer A charged particle beam irradiation apparatus characterized in that, when there are a plurality of layers that satisfy a first condition that is equal to or less than a beam loss amount at the time of energy change, the layer with the highest unirradiated dose is determined as the next irradiation layer. The charged particle beam irradiation apparatus according to claim 1,
When it is determined that there is a layer that can be irradiated within the same period when irradiation with a certain energy is completed, the irradiation order determination unit is expected to remain after irradiation of the next irradiation layer If there is no layer that satisfies the first condition that is less than or equal to the amount of beam loss at the time of energy change, the amount of orbital beam charge that is expected to remain after irradiation based on the amount of orbital beam at that time is the beam at the time of energy change. When there is a combination of layers satisfying the second condition that is less than or equal to the loss amount, the charged particle beam irradiation apparatus determines one layer in the combination that satisfies the second condition as a next irradiation layer. The charged particle beam irradiation apparatus according to claim 1,
When it is determined that there is a layer that can be irradiated within the same period when irradiation with a certain energy is completed, the irradiation order determination unit is expected to remain after irradiation of the next irradiation layer If there is no layer that satisfies the first condition that is less than or equal to the amount of beam loss at the time of energy change, the amount of orbital beam charge that is expected to remain after irradiation based on the amount of orbital beam at that time is the beam at the time of energy change. A charged particle beam irradiation apparatus characterized in that, when there are a plurality of combinations of layers that satisfy the second condition that is less than or equal to a loss amount, a combination that is predicted to minimize a beam that is not used for irradiation is selected.

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